function s1_goto_dir(){
  cd "$1"
}
function s2_touch_empty_file_with_given_name(){
  touch "$1"
}
function s3_make_directories(){
  mkdir -p ./projects/{git/,backup/}
}
function s4_create_6_files(){
  touch ./projects/linux{1,2}_{centos,redhat,c_programming}
}
function s5_make_directories_in_git(){
  mkdir ./projects/git/linux{1,2}
}
function s6_move_files_to_dir_1_or_2(){
  mv ./projects/linux1* ./projects/git/linux1 && mv ./projects/linux2* ./projects/git/linux2
}
function s7_create_package_and_compress(){
  tar -czvf ./projects/backup/git.tar.gz ./projects/git
}
function s8_delete_dir_git(){
  rm -rf ./projects/git
}
function s9_recover_from_git_tar_gz_backup(){
  tar -zxvf ./projects/backup/git.tar.gz ./projects/
}
function s10_create_package_and_compress(){
  tar -jcvf ./projects/backup/git.tar.bz2 ./projects/git
}
function s11_find_and_sort_alphabetically_all_created_files_and_dirs(){
  find ./projects | sort
}
function s12_get_next_15_minutes_boundary(){
  date -d "@$(($(date +%s) - $(date +%s)%900 + 900))" +"%Y-%m-%d_%H:%M:%S"
}